Medical Definition of Serum

Serum: The clear liquid that can be separated from
clotted blood. Serum differs from plasma, the liquid portion of
normal unclotted blood containing the red and white cells and
platelets. It is the clot that makes the difference between serum
and plasma.

Terms in this dictionary with the word “serum” include
maternal serum alpha-fetoprotein (MSAFP), serum glutamic oxaloacetic
transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), and
serum hepatitis.

The term “serum” also is used to designate any normal or
pathological fluid that resembles serum as, for example, the fluid in
a blister.

“Serum” is a Latin word that refers to the
“whey”, the watery liquid that separates
from the curds in the process of cheesemaking.